The invention relates to open-end rotor spinning machines, having a plurality of spinning units that each contain a spinning rotor that is arranged in a rotor housing connected to a vacuum source. The spinning units include at least one yarn-deflecting point that is formed by at least one false-twisting edge being assigned to this yarn withdrawal duct, and a movable servicing apparatus that can be applied to the individual spinning units which is equipped with devices for the feeding of a yarn end to the yarn withdrawal duct.
In German Patent No. 23 66 255, an open-end rotor spinning machine of the initially mentioned type is shown in which the yarn withdrawal duct consists of a yarn withdrawal nozzle to which a one-piece tube is connected that has a bend. For the piecing, a yarn end is applied to this yarn withdrawal tube which is then sucked into the yarn withdrawal duct because of the vacuum existing in the spinning rotor, and is subsequently applied to the spinning rotor.
French Patent No. 25 32 665 shows replacing the deflecting point of the yarn withdrawal duct by an insert that forms at least one false-twisting edge. By means of these types of false-twisting edges, the twist of the spun yarn can be reduced and/or the danger of yarn breakages can be diminished. The false-twisting edges that project into the moving path of the yarn, however, impair the returning of the yarn end for a piecing. In addition, in the area of the false-twisting edges, a rubbing-off of the yarn is created, in which case the rubbed-off parts may deposit in this area. As a result, the returning of the yarn end during the piecing is impaired, and the danger is created that these rubbed-off parts are sucked back into the spinning rotor and cause disturbances, particularly during the piecing. It is therefore necessary that a yarn withdrawal tube of this type be cleaned before a piecing, in which case, however, the area of the false-twisting edges is not easily accessible for a cleaning.
An object of the invention is to provide an open-end rotor spinning machine in which the use of false-twisting edges does not result in an impairment of the returning of a yarn end.
Another object of the invention is to provide an open-end rotor spinning machine having false-twisting edges in which costly cleaning operations are not required. Yet another object of the invention is to provide false-twisting edges which are easily accessible, and therefore easily cleaned.
Still a further object of the invention is to provide false-twisting edges being disposed such that any impurities created at the false-twisting edges are less apt to accumulate and impair spinning or piecing processes.
These objects are achieved by providing an open-end spinning machine having a deflecting component having at least one false-twisting edge downstream from a yarn withdrawal duct. A yarn returning element returns a yarn end to the yarn withdrawal duct past the deflecting component in a piecing operation such that the yarn is deflected less during piecing than during spinning.
Using this arrangement, it is possible to arrange the deflecting component having the false-twisting edges in the open so that rubbed-off yarn parts that occur in this area do not remain in the area of the false-twisting edges. In certain preferred embodiments, a yarn end bypasses the component containing the false-twisting edges during a piecing as the yarn is fed to the mouth of the straight yarn withdrawal duct, such that there is no danger that the returning yarn end can become caught in the area of the false-twisting edges. In addition, the advantage is obtained that the component containing the false-twisting edges can be held independently of the yarn withdrawal duct so that, if required, it alone can be replaced.
According to other advantageous features of certain preferred embodiments of the invention, in order to facilitate the returning of the yarn end, a guiding element is provided that extends to a covering that covers the spinning units toward the outside. The guiding element is arranged behind the deflecting component containing the at least one false-twisting edge. This guiding element is used for aligning the yarn end with the mouth of the short, straight yarn withdrawal duct. In certain embodiments, the distance between the guiding element and the mouth of the yarn withdrawal duct can be bridged with sealing devices that form a connecting duct. Particularly, when the guiding element is developed as a tube that has the dimensions of a conventional yarn withdrawal tube, it is possible to create the same conditions as in the case of previous yarn withdrawal tubes for the sucking-back of a yarn end required for the piecing.
According to other advantageous features of certain preferred embodiments of the invention, it is provided that the deflecting component is held so that it can be adjusted between an operating spinning position and a piecing position. In these embodiments, the at least one false-twisting edge is located on the outside of an extension of the yarn withdrawal duct in the piecing position. As a result, it is ensured that the returning of a yarn end is not impaired by the false-twisting edges. In a particularly advantageous contemplated embodiment, it is further provided that connecting devices for connecting the yarn withdrawal duct with the guiding element are provided. When the deflecting component is located in the piecing position, the connecting devices can be introduced between the mouth of the yarn withdrawal duct and the guiding element, replacing the deflecting component, and establishing an approximately airtight connection between the guiding element and the yarn withdrawal duct.
In certain preferred embodiments, these connecting devices may be divided by a dividing seam extending in longitudinal direction of the yarn, so that after the piecing, they are moved out from between the area of the mouth of the yarn withdrawal duct and the guiding element. The false-twisting edges are then brought into the operating position. In this operating position, the area below the false-twisting edges will then be in the open so that rubbed-off yarn parts cannot deposit in the area of the yarn movement. In these embodiments, it is possible to create the same conditions for the piecing that normally exist in spinning units with closed yarn withdrawal tubes having a uniform cross-section. It is contemplated that the connecting devices for connecting the yarn withdrawal duct with the guiding element are a component of each spinning unit and are adjusted by the servicing device during the piecing. However, it is also contemplated to make these devices components of the servicing device so only one is required for one open-end spinning machine.
According to other advantageous features of certain preferred embodiments of the invention, it is provided that each spinning unit is equipped with air blowing devices for generating an air current that is aimed essentially in the direction of the mouth of the yarn withdrawal duct. The air blowing devices can be switched on and off by the movable servicing device. As a result, each spinning unit is equipped with pneumatic auxiliary transport devices by means of which the transport of yarn can be promoted from the feeding devices of the servicing device to the mouth of the yarn withdrawal duct.
According to other advantageous features of certain preferred embodiments of the invention, it is provided that the movable servicing device is equipped with devices for generating a blowing air current aimed at the mouth of the yarn withdrawal duct. In these embodiments, any other guiding elements or the like that guide the yarn behind the deflecting component are not necessary.
Since the deflecting component having the false-twisting edges may be arranged in the open, it is provided in certain preferred embodiments of the invention that collecting devices are arranged below the deflecting component in the open at least during the normal spinning operation. The collecting devices are used for the catching and/or removing of material that is detached from the yarn. These embodiments prevent contamination of the spinning units by rubbed-off pieces of yarn.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.